Seat belt tensioner

ABSTRACT

The disclosed seat belt tensioner for a seat belt system may comprise a seat belt spindle, a gearwheel connected to the seat belt spindle, and a latching pawl for locking the seat belt spindle in the tensioned position by engaging in the teeth of the gearwheel. The latching pawl may be configured to be brought into a first pawl position for blocking the gearwheel in the seat belt unrolling direction and into a second pawl position for blocking the gearwheel in the seat belt-tensioning direction of rotation. The latching pawl may also be configured to perform a first pivot-over operation from the first pawl position into the second pawl position and to perform a second pivot-over operation from the second pawl position into the first pawl position when the gearwheel exerts a force on the latching pawl that exceeds a predetermined force required for the respective pivoting-over operation.

BACKGROUND

The invention relates to a seat belt tensioner with a latching pawlwhich, after the end of a tensioning operation, locks a seat beltspindle of a seat belt system in the tensioned position by engaging inthe teeth of a gearwheel connected to the seat belt spindle.

A seat belt tensioner of this type is disclosed in international PCTapplication publication WO 02/046005 A1, published Jun. 12, 2002 andincorporated by reference herein. This seat belt tensioner has ablocking device with a latching pawl, which is activated by means of anactivating device. The activation takes place in such a manner that,after the end of a seat belt-tensioning operation, the latching pawlblocks the seat belt spindle of the seat belt system in the tensionedposition by having the latching pawl engage in the teeth of a gearwheelthat is connected to the seat belt spindle. To release the latchingpawl, the gearwheel is first operated in the seat belt-tensioningdirection of rotation so that the latching pawl can disengaged from thegearwheel. The latching pawl is subsequently pivoted away from thegearwheel.

SUMMARY

The present application is based on the object of specifying a seat belttensioner, which can be manufactured cost-effectively and ensures a highcomfort of use for the vehicle occupant.

According to the present application, this object is achieved bystarting with a seat belt tensioner of the type indicated above andadding, for example, the feature of a latching pawl configured in such amanner that it can be brought into a first pawl position and into asecond pawl position.

It is to be understood that both the foregoing general description andthe following detailed descriptions are exemplary and explanatory only,and are not restrictive of the invention as claimed,

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become apparent from the following description, appendedclaims, and the accompanying exemplary embodiments shown in thedrawings, which are briefly described below.

FIG. 1 is a perspective view of a seat belt tensioner according to anembodiment of the present invention.

FIG. 2 is a detailed view of a first force transmission path accordingto an embodiment of the invention.

FIG. 3 is a detailed view of the operation of a sliding clutch formed bya pawl carrier, a disk cam, and a coupling wheel.

FIG. 4 is a view of the pawl carrier without the coupling wheel or diskcam attached to expose the torsion ring.

FIG. 5 is a detailed view of a spindle clutch.

FIG. 6 shows a seat belt spindle together with the spindle clutch afterthe installation on an installation plate.

FIG. 7 is a detailed view of a planetary gear according to an embodimentof the present invention.

FIG. 8 shows the construction and the operation of a blocking deviceaccording to an embodiment of the present invention.

FIG. 9 shows the lower view of the operation of the blocking device witha latching pawl in a first pawl position.

FIG. 10 shows the upper view of the operation of the blocking devicewith the latching pawl in a second pawl position.

FIG. 11 shows an overload clutch that can be arranged between the pawlteeth of the seat belt spindle and the seat belt spindle.

FIG. 12 shows the operation of the seat belt tensioner when the drivemotor is operated in the seat belt-tensioning direction of rotation.

FIG. 13 shows the resultant positions of the latching pawl, the diskcam, and the sliding clutch pawl after an accident where thepredetermined seat belt-extraction force has been exceeded.

FIG. 14 shows the latching pawl that is pivoted back into its first pawlposition after an accident where the predetermined seat belt-extractionforce has been exceeded.

FIG. 15 shows a detailed view of an assembly comprising a connectingrod, a connecting rod pin, a friction element, and the latching pawlaccording to an embodiment of the present invention.

DETAILED DESCRIPTION

As disclosed herein, the latching pawl can be designed so that it can bebrought into a first pawl position and into a second pawl position. Inits first pawl position, the latching pawl blocks the gearwheel in theseat belt-unrolling direction while, in its second pawl position, thelatching pawl blocks the gearwheel in the seat belt-tensioning directionof rotation. The latching pawl may be mounted, preferably in aspring-loaded manner, such that it is pivoted over from the first pawlposition into the second pawl position and vice versa when the gearwheelexerts a force on the latching pawl that exceeds a pivoting-over forcerequired for the respective pivoting-over process.

One advantage of the seat belt tensioner according to the applicationcan be found in the fact that the tensioner manages without anadditional activating device connected to the latching pawl, i.e.,without an additional actuator, because the switching “on” and “off” ofthe latching pawl can be brought about solely with the gearwheel. Thereason is because the gearwheel can be used to bring the latching pawlinto the respectively required pawl position. Owing to the fact that anadditional actuator is not required, the seat belt tensioner accordingto the disclosure can be produced very cost-effectively.

Another advantage of the seat belt tensioner according to the presentapplication can be found in the fact that the blocking device cannotreadily be destroyed during the operation by the latching pawl becausethe latching pawl is pivoted when the force of the gearwheel that actson the latching pawl exceeds a predetermined maximum force.

A third possible advantage of the present seat belt tensioner may bethat the latching pawl can be released without an increase in the seatbelt-restraining force acting on the vehicle occupant. All that needs tobe done for this is for the gearwheel to be driven in the seatbelt-unrolling direction with a driving force, which exceeds thepredetermined “pivoting-over force” of the latching pawl.

The latching pawl may be preferably mounted in such a manner that thepivoting-over of the latching pawl from the first pawl position into thesecond pawl position and/or vice versa can be triggered by the motorforce of the drive motor of the seat belt tensioner. To this end, thedrive motor is connected to the gearwheel. An advantage of thisconfiguration of the seat belt tensioner may be that the drive motor,which may be present in any case, can be used to shift the latchingpawl. For example, after the latching pawl has been shifted due to anaccident from the first pawl position into the second pawl position, theseat belt tensioner can be “reactivated” again by moving the latchingpawl back with the drive motor from the second pawl position into thefirst pawl position again. If the seat belt has been tensioned with theseat belt tensioner without subsequently an accident actually happeningand without the latching pawl having been brought into the second pawlposition, then the blocking device can advantageously also be unblockedin a corresponding manner by the drive motor by the latching pawl beingdisplaced by the drive motor from the first pawl position into thesecond pawl position. Thus, the “release peak” occurring in the ease ofpreviously known seat belt tensioners does not occur here.

The latching pawl may be preferably held in such a manner that, whenthere is a predetermined seat belt-extraction force that bears againstthe shoulder of the vehicle occupant and may be preferably between about1000 N and about 3000 N (more preferably about 2000 N), the latchingpawl is pivoted from the first pawl position into the second pawlposition. This ensures that the seat belt can unroll when this seatbelt-extraction force is reached, thus avoiding injuries to the vehicleoccupant. The unrolling of the seat belt can be predetermined orcontrolled, for example, by means of a torsion bar or the like. As analternative or in addition, the unrolling of the seat belt may also becontrolled by the drive motor of the seat belt tensioner.

The latching pawl can be held pivotably, for example, in accordance witha toggle-lever principle in order to permit it to be pivoted from thefirst pawl position into the second pawl position and vice versa.

As an alternative, the pivot pin of the latching pawl may be arranged inan elongated hole of the latching pawl in such a manner that thelatching pawl can be pivoted in a direction of rotation about the pivotpin and can be deflected radially to the pivot pin along a guide slotformed by the elongated hole.

At least one latching pawl spring, which pivots the latching pawl towardthe gearwheel, may preferably interact with the latching pawl.

It may also be regarded as advantageous if the seat belt tensioner has amechanical automatic gear, which shifts automatically as a function ofload. An advantage of an automatic gear can be seen by the fact that theautomatic gear does not require an electric control device, which causesthe gear to shift, because the gear is shifted automatically as afunction of load. Furthermore, a mechanical automatic gear manageswithout electric displacement elements, for example, solenoids orpyrotechnic actuating elements.

It can be regarded as advantageous if the seat belt tensioner iscompletely reversible. A reversible seat belt tensioner makes itpossible to use the tensioner, after a first accident event in which theseat belt has been tensioned for a first time by the seat belttensioner, to tension the seat belt one or more further times. Areversible seat belt tensioner is therefore also capable of use in thesituation referred to as a “second impact” (or further accident events).

The automatic gear may preferably have at least two speeds and has afirst force transmission path for a first speed with a firsttransmission ratio and at least one further force transmission path fora second speed and a transmission ratio that is larger than the firsttransmission ratio.

The automatic gear may preferably have a connecting gearwheel, which isdriven by the drive motor of the seat belt tensioner and interacts bothwith the first force transmission path and with the second forcetransmission path. The connecting gearwheel can advantageously form thegearwheel with which the latching pawl of the blocking device interacts.

A shifting from the first force transmission path to the second forcetransmission path can be achieved in a particularly simple, andtherefore advantageous, manner if the first force transmission pathcomprises a sliding clutch, which disengages when a predeterminedswitching-off moment is exceeded, so that the further force transmissionpath is activated. The predetermined switching-off moment of the slidingclutch may be preferably dimensioned in such a manner that itcorresponds to a seat belt force on the shoulder of the vehicle occupantof between about 200 and about 250 Newtons.

The first force transmission path can be formed in a cost-effective, andtherefore advantageous, manner with the sliding clutch, a coupling wheelconnected to the sliding clutch, and a spindle clutch toothed ringconnected to the seat belt spindle and the coupling wheel.

The sliding clutch may preferably have a pawl carrier, which is mountedrotatably coaxially with the connecting gearwheel. A sliding clutch pawlcan preferably be mounted pivotably on the pawl carrier in such a mannerthat it can be pivoted into a coupling position and into a disengagingposition. In its coupling position, the sliding clutch pawl couples thepawl carrier and the connecting gearwheel. In its disengaging position,the sliding clutch pawl is ineffective with regard to the couplingbetween the connecting gearwheel and the pawl carrier.

The term “seat belt-tensioning direction of rotation” below indicatesthe direction of rotation in which the seat belt is retracted and istherefore tensioned. With regard to the direction of rotation, it isfocused on the action in which the particular rotation has on the seatbelt. For example, the drive motor and the seat belt spindle alwaysrotate in opposite directions of rotation because of the automatic gearbut nevertheless they each both have the “seat belt-tensioning directionof rotation” during the tensioning of the seat belt. In a correspondingmanner, the term “seat belt-unrolling direction” below is understood asmeaning the opposite direction of rotation in which the seat belt isunrolled from the seat belt spindle.

The sliding clutch may preferably have a disk cam, which prevents thesliding clutch pawl, after it has reached its disengaging position, fromautomatically passing again into the coupling position. This has theeffect that, after the automatic gear has shifted up from the firstspeed into the second speed, i.e., from the first force transmissionpath to the second force transmission path, a shifting back from thesecond speed to the first speed is prevented as long as such a shiftingback is not desired and permitted.

The disk cam and the pawl carrier can be rotated, for example, by apredetermined angle of rotation relative to each other. As soon as thesliding clutch pawl has reached its disengaging position, the disk cammay preferably be rotated by a spring into a blockade position in whichit holds the sliding clutch pawl in the disengaging position andprevents the sliding clutch pawl from being reinserted into theconnecting gearwheel.

In addition to the sliding clutch pawl already mentioned—called the“first” sliding clutch pawl below—the sliding clutch may preferably havea second sliding clutch pawl. The function of the second sliding clutchpawl is to assist the first sliding clutch pawl in the forcetransmission. The two sliding clutch pawls can be preferably engaged anddisengaged together. The second sliding clutch pawl can be mountedpivotably, for example, on the pawl carrier.

The two sliding clutch pawls may be preferably in each case preloaded inthe insertion direction with respect to the connecting wheel. For costreasons, this preloading of the two sliding clutch pawls is broughtabout by one and the same pivoting spring.

The seat belt spindle and the automatic gear can be preferably connectedto each other with a spindle clutch. The spindle clutch may bepreferably configured in such a manner that it engages when the drivemotor rotates in the seat belt-tensioning direction of rotation anddisengages with a freedom from load when the drive motor rotates in theseat belt-unrolling direction of rotation.

The spindle clutch may preferably have spindle clutch pawls, which arearranged in such a manner that they are inserted into the pawl teeth ofthe seat belt spindle as soon as the spindle clutch toothed ring rotatesin the seat belt-tensioning direction of rotation. As a result the seatbelt spindle and the spindle clutch toothed ring couple to each other ina rotationally fixed manner.

In addition, the spindle clutch pawls may be preferably arranged in sucha manner that they are pivoted out of the pawl teeth of the seat beltspindle as soon as the spindle clutch toothed ring rotates in the seatbelt-unrolling direction and there is a freedom from load. By means ofsuch a pivoting-out of the spindle clutch pawls, the coupling connectionbetween the seat belt spindle and the spindle clutch toothed ring can beseparated so that the seat belt spindle can subsequently be rotatedfreely again. In other words, the spindle clutch pawls therefore onlycouple in the seat belt-tensioning direction of rotation but not in theseat belt-unrolling direction.

In order to ensure that the spindle clutch pawls are inserted completelyinto the pawl teeth of the seat belt spindle, the spindle clutch maypreferably have a synchronization pawl, which is inserted into the pawlteeth of the seat belt spindle. The seat belt spindle and the spindleclutch toothed ring are thereby aligned with each other before thespindle clutch pawls engage in the pawl teeth of the seat belt spindle.The function of the synchronization pawl is therefore to force apredetermined relative position between the spindle clutch toothed ringand the spindle clutch pawls before the spindle clutch pawls can beinserted into the pawl teeth of the seat belt spindle.

The spindle clutch pawls and the synchronization pawl can preferably beheld pivotably in or on a spindle clutch housing, which is alignedcoaxially with the seat belt spindle and is mounted rotatably inrelation to the seat belt spindle. The spindle clutch housing may be,for example, of a two-part design and may have a spindle clutch carrierand a planet carrier connected thereto.

If the automatic gear has a planetary gear, it can be regarded asadvantageous if the spindle clutch housing has at least one fasteningpoint for the rotatable fastening of at least one planet wheel of theplanetary gear. For example, the spindle clutch housing can have threefastening points for three planet wheels. The fastening points for theplanet wheels may be formed, for example, by pins on which the planetwheels of the planetary gear are rotatably mounted.

A planetary gear may be preferably arranged in the further forcetransmission path. The planetary gear can preferably revolve in a mannerfree from force transmission when the sliding clutch is engaged and,only when the sliding clutch is disengaged, is it used for the forcetransmission. The planetary gear then provides the second speed of thegear.

In order to make it possible for the planetary gear to revolve in amanner free from force transmission, said planetary gear may preferablyhave a crown wheel, which is driven by at least one planet wheel. Aninternal sun wheel serves, for example, to drive the at least one planetwheel. An external sun wheel, for example, which is driven by theconnecting gearwheel is connected to the internal sun wheel. Theinternal and external sun wheels may be formed by two separate wheels.As an alternative, the two sun wheels may also be formed by an integralwheel.

The planetary gear may preferably have a planetary clutch pawl thatinteracts with the crown wheel, that permits a rotation of the crownwheel along a predetermined crown wheel direction of rotation, and thatblocks a rotation of the crown wheel counter to the predeterminedcrown-wheel direction of rotation. The revolving of the planetary gearin a manner free from transmission when the sliding clutch is engagedand with the force transmission when the sliding clutch is disengagedcan therefore be ensured with the planetary clutch pawl.

In order to activate the planetary clutch pawl, it is pivoted toward thecrown wheel, for example, by a planetary clutch pawl spring.

In order to prevent the gear from being destroyed in the event of avehicle accident by the high seat belt-restraining forces occurringbecause of the accident, it may be regarded as advantageous if anoverload clutch is arranged between the gear and the seat belt spindleand transmits torques up to a predetermined maximum torque and, when themaximum torque is exceeded, disengages. The overload clutch thereforeavoids critical or excessive torques from being transmitted by the seatbelt spindle to the gear.

The overload clutch can preferably be formed by two coupling elements,which form a force-locked connection between the gear and the seat beltspindle. The force-locked connection is designed in such a manner thatit is automatically cancelled when the predetermined maximum torque isexceeded.

In a particularly simple, and therefore advantageous, manner, theoverload clutch can be formed by tapered coupling elements.Specifically, the first coupling element is formed, for example, by aninternal taper and the second coupling element is formed by an externaltaper.

To explain the invention, FIGS. 1 to 15 show various exemplaryembodiments for the seat belt tensioner according to the presentapplication. These embodiments of the present invention will now bedescribed with reference to those drawings.

FIG. 1 illustrates a seat belt tensioner 1 for tensioning a seat belt 2.The seat belt tensioner has a drive motor 3, which is connected by itsmotor pinion 31 to an automatic gear 4. The automatic gear 4 is alsoconnected to a seat belt spindle 5 as a seat belt roller.

As to the automatic gear 4, FIG. 1 shows a connecting gearwheel 10,which is connected to a first force transmission path 6 and a secondforce transmission path 7 of the automatic gear 4.

In reference to the first force transmission path 6, FIG. 1 shows aspindle clutch toothed ring 61, which is coupled to the connectinggearwheel 10. In regards to the second force transmission path 7, FIG. 1shows a planetary gear or planet wheel gear 71 with an external sunwheel 711. The external sun wheel 711 is in engagement with theconnecting gearwheel 10. An internal sun wheel 712, which interacts withplanet wheels that are not visible in FIG. 1, is connected to theexternal sun wheel 711. The planet wheel gear 71 also has a crown wheel713, in which its operation will be explained further below.

FIG. 1 also shows a blocking device 8 with a latching pawl 81. Theblocking device 8 blocks the connecting gearwheel 10 after seat belttensioning has taken place so that the drive motor 3 can be switchedoff. After the seat belt tensioning has taken place, the blocking device8 can be deactivated again by the drive motor 3 being switched at leasttemporarily into the seat belt-unrolling direction.

The drive motor 3 and the automatic gear 4 are mounted on aninstallation plate 9.

FIG. 2 illustrates the first force transmission path 6 in detail. Itshows the spindle clutch toothed ring 61, which is connected to the seatbelt spindle 5 via a spindle clutch 51. The spindle clutch toothed ring61 is also in engagement with a coupling wheel 62.

The disk cam 63 is fitted rotatably on a pawl carrier 64, which isarranged coaxially with the connecting gearwheel 10. The pawl carrier 64and the connecting gearwheel 10 are mounted rotatably relative to eachother. The coupling wheel 62 is connected in a rotationally fixed mannerto the pawl carrier 64, for example by means of a claw clutch.

A first sliding clutch pawl 65 is mounted pivotably about a pivot pin651 on the pawl carrier 64. The sliding clutch pawl 65 is deflected bymeans of a pivoting spring 641, which is fastened on the pawl carrier 64in such a manner that it is in engagement with the internal teeth of theconnecting gearwheel 10. In this case, the sliding clutch pawl 65 isaligned in such a manner that a force transmission occurs between theconnecting gearwheel 10 and the pawl carrier 64 along the seatbelt-tensioning direction of rotation of the seat belt tensioner 1. Theseat belt-tensioning direction of rotation is identified in FIG. 2 bythe designation S.

It can be seen in FIG. 2 that the disk cam 63 has a cam 631, whichinteracts with the sliding clutch pawl 65. The function of the cam 631is to bear against the sliding clutch pawl 65 if the sliding clutch R(formed by the sliding clutch pawl 65, the pawl carrier 64, and the diskcam 63) is engaged.

In the position as illustrated in FIG. 2 of the sliding clutch pawl 65,a direct force transmission takes place between the motor pinion 31, theconnecting gearwheel 10, the coupling wheel 62, the spindle clutchtoothed ring 61 and the seat belt spindle 5 since the spindle clutch 51is engaged. The operation of the spindle clutch 51 will be explainedfurther below.

The operation of the sliding clutch R formed by the pawl carrier 64, thedisk cam 63, and the coupling wheel 62 is shown in FIG. 3 once again ina detailed illustration. As soon as the torque to be transmitted exceedsa predetermined load moment during a rotational movement along the seatbelt-tensioning direction S, the sliding clutch is disengaged by thesliding clutch pawl 65 being pivoted inward counter to the spring forceof the pivoting spring 641. When a pivoting movement of this typeoccurs, the disk cam 63 will rotate along the arrow direction P1relative to the pawl carrier 64 so that the cam 631 is guided past thesliding clutch pawl 65. In the state illustrated in FIG. 3, the slidingclutch R is therefore disengaged since the sliding clutch pawl 65 haspassed into its disengaging position.

In addition to the sliding clutch pawl 65, there can moreover be asecond sliding clutch pawl 69 as shown in FIG. 3. The function of thesecond sliding clutch pawl 69 is to assist the first sliding clutch pawl65 in the force transmission. The second sliding clutch pawl 69 isarranged in such a manner that it is engaged and disengaged togetherwith the first sliding clutch pawl 65.

FIG. 4 shows a torsion spring 642, which is fastened on the pawl carrier64 and places the disk cam 63 (not shown in FIG. 4) under a preload onthe pawl carrier 64. Due to the torsion spring 642, the disk cam 63 isrotated along the direction of rotation P1 illustrated in FIG. 3 as soonas the sliding clutch pawl 65 has passed into its disengaging position.

The rotation of the disk cam 63 with the cam 631 achieves the effectthat the sliding clutch pawl 65, after it has reached its disengagingposition illustrated in FIG. 3, can no longer automatically pass againinto the coupling position. Thus, the sliding clutch pawl 65 remainsdisengaged after a disengagement has taken place.

In FIG. 5, the spindle clutch 51, already mentioned in conjunction withFIG. 2, of the seat bell spindle 5 is shown in detail. Three spindleclutch pawls 52, which are held pivotably in a spindle clutch housing53, can be seen. Each of the three spindle clutch pawls 52 has in eachcase an external cam 522, which is always guided into an associated,inside-edge recess 611 in the spindle clutch toothed ring 61.

In addition, each of the spindle clutch pawls 52 has two inner claws521, which engage in the pawl teeth 54 of the seat belt spindle 5. Thepawl teeth 54 of the seat belt spindle 5 are connected integrally, forexample, to the seat belt spindle 5. As can be gathered from FIG. 5,when the spindle clutch toothed ring 61 is driven in the seatbelt-tensioning direction of rotation S, the internal claws 521 willengage in the pawl teeth 54 of the seat belt spindle 5 so that acoupling between the seat belt spindle 5 and the spindle clutch toothedring 61 comes about.

A synchronization pawl 55 can also be seen in FIG. 5. The function ofthe synchronization pawl 55 is to bring about a coupling between theseat belt spindle 5 and the spindle clutch toothed ring 61 before thespindle clutch pawls 52 pivot in toward the direction of the pawl teeth54 of the seat belt spindle 5 and engage. The synchronization pawl 55therefore brings about an adjustment of the spindle clutch pawls 52 withrespect to the pawl teeth 54 of the seat belt spindle 5 so that adefined engagement of the spindle clutch pawls 52 in the pawl teeth 54of the seat belt spindle 5 can take place. A mutual blocking of thespindle clutch pawls 52 is therefore reliably avoided by thesynchronization pawl 55. If just a single spindle clutch pawl 52 isused, the synchronization pawl 55 could be omitted.

In FIG. 5, three holes 531 can be seen in the spindle housing 53. Pins,which bear the planet wheels of the planet wheel gear 71 according toFIG. 1, are inserted into the holes 531. The pins and the planet wheelsof the planet wheel gear 71 are not illustrated in FIG. 5.

FIG. 5 also shows a brake shoe 532, which is pressed radially outward bymeans of a brake shoe spring 533 so that it always bears in a bearinghole of the installation plate 9. The function of the brake shoe 532 isto prevent the spindle clutch housing 53 from chattering in relation tothe installation plate 9. By means of the brake shoe 532, themanufacturing tolerances in the manufacturing of the spindle clutchhousing 53 and of the installation plate 9 are compensated for. Thebrake shoe spring 533 also has a further function, namely of keeping thesynchronization pawl 55 in a disengaged position in relation to the pawlteeth 54. However, when the drive motor 3 is switched on, the force ofthe brake shoe spring 533 is overcome by the synchronization pawl 55 sothat the synchronization pawl can be inserted into the pawl teeth 54.

FIG. 6 once again shows the seat belt spindle 5 together with thespindle clutch 51 after the installation on the installation plate 9.

FIG. 7 shows in detail the planetary gear 71 according to FIG. 1. Theexternal sun wheel 711 and the internal sun wheel 712, which isconnected thereto and drives three planet wheels of the planetary gear71, can be seen. Of the three planet wheels, only one planet wheel 714can be seen in FIG. 7. The planet wheel 714 and the two other planetwheels are held on pins which are held in the holes 531 of the spindleclutch housing 53 according to FIG. 5.

The crown wheel 713, which interacts with a planetary clutch pawl 715,can also be seen in FIG. 7. The planetary clutch pawl 715 has the effectof enabling the crown wheel 713 to be rotated exclusively counter to thedirection of rotation P2. In the process, the planetary clutch pawl 715ratchets along the external teeth of the crown wheel 713. Along thedirection of rotation P2, the planetary clutch pawl 715 blocks arotation of the crown wheel 713.

The planetary clutch pawl 715 is pressed toward the crown wheel 713 by aplanetary clutch pawl spring 716 so that the locking effect (alreadyexplained) by the planetary clutch pawl 715 is ensured.

The function of the planetary clutch pawl 715 is to permit the externalsun wheel 711, the internal sun wheel 712, and the planet wheel 714 ofthe planetary gear 71 to revolve without a force transmission to theseat belt spindle 5 occurring. A revolving of the planetary gear 71 in amanner free from force transmission then occurs if the sliding clutchaccording to FIG. 1 is engaged and the force transmission takes placealong the first force transmission path 6.

In conjunction with FIGS. 8 to 10, the construction and the operation ofthe blocking device 8 according to FIG. 1 will now be explained. FIG. 8shows the latching pawl 81, which is held rotatably on a bearing pin 82.The latching pawl 81 is guided on the bearing pin 82 via an elongatedhole 83 (as seen in FIG. 9).

A latching pawl spring 84 is connected to the latching pawl 81. Thefunction of the latching pawl spring 84 is to press the latching pawl 81toward the connecting gearwheel 10.

The object of the latching pawl 81 is to keep the seat belt 2 in thetensioned position after the seat belt has been tensioned by the drivemotor 3. The latching pawl 81 brings this about by the fact that itprevents the connecting gearwheel 10 from rotating back in the seatbelt-unrolling direction. The latching pawl 81 therefore blocks theconnecting gearwheel 10 in the seat belt-unrolling direction A as shownin FIG. 9.

It can also be seen in FIG. 9 that it is possible, owing to themultiplicity of latching teeth on the outside of the connectinggearwheel 10 to keep the seat belt 2 in virtually any position using thelatching pawl 81. An undesirable yielding of the seat belt 2 due to theplay in the blocking device 8 is therefore limited. In the case of theexemplary embodiment, the undesirable yielding of the seat belt 2 issmaller than 1.5 degrees with regard to the angle of rotation of theseat belt spindle 5.

In the event of an accident, the seat belt-extraction force acting onthe seat belt 2 will increase severely as soon as the vehicle occupantheld by the seat belt 2 presses against the seat belt. In order then topermit the seat belt 2 to yield so that injuries due to the seat beltare avoided, the latching pawl 81 is pivoted (the pivoting direction U)from the first pawl position illustrated in FIG. 9 (the latching pawl 81faces away from the motor pinion 31) into a second pawl positionillustrated in FIG. 10 (the latching pawl 81 faces the motor pinion 31)when a predetermined maximum seat belt-extraction force is exceeded. Thepredetermined seat belt-extraction force may be preferably between about1000 and about 3000 Newtons, more preferably about 2000 Newtons withregard to the seat belt force on the shoulder of the vehicle occupant.

The unrolling speed of the seat belt can be controlled, for example,with the drive motor 3 since its motor pinion 31 is always in engagementwith the connecting gearwheel 10. Thus, with the drive motor 3 beingenergized in the seat belt-tensioning direction of rotation, theunrolling of the seat belt can be stopped.

A pivoting of the latching pawl 81 is possible because the latching pawl81 is held in an elastically resilient manner in the elongated hole 83by the latching pawl spring 84. When the predetermined seatbelt-extraction force is exceeded, the latching pawl 81 is thereforepressed away from the connecting gearwheel 10 counter to the restoringforce of the latching pawl spring 84. This permits the latching pawl 81to pivot or flip over in such a manner that it is transferred into thesecond pawl position illustrated in FIG. 10 (the pivoting direction U inFIGS. 9 and 10). The latching pawl 81 pivots together with a latchingblock 85. This takes place as follows: when the predetermined seatbelt-extraction force is reached, the latching pawl 81 is pressed in thedirection of the latching block 85. In the process, a cam 86 of thelatching pawl 81 strikes against a stop 87 of the latching block 85. Asa result, the latching block 85 then pivots counterclockwise (cf. FIG.8) about the bearing pin 82 so that the latching pawl 81 is released forpivoting-over according to the pivoting direction U and then thepivoting-over takes place.

In the second pawl position illustrated in FIG. 10 (the latching pawl 81faces the motor pinion 31), the latching pawl 81 no longer prevents anunrolling of the seat belt 2. Thus, the seat belt 2 can unroll when themotor drive 3 is switched off. In the second pawl position, the latchingpawl only slides along the run on the collar of the connecting gearwheel10. This makes it possible to unroll the seat belt 2 in a specificmanner by means of further devices, for example, a torsion bar, suchthat there is a reduced seat belt-restraining force on the vehicleoccupant.

In conjunction with FIGS. 9 and 10, it should be mentioned that FIG. 9shows the connecting gearwheel 10 from its lower side and FIG. 10 showsit from its upper side. In addition, the crown wheel 713 and the spindleclutch housing 53 can be seen from the lower side in FIG. 9.

Since the components of the seat belt tensioner 1 have been explained indetail in conjunction with FIGS. 1 to 10, the interaction of thecomponents in the event of a vehicle accident will now be explained onceagain for better comprehension.

In the event of a vehicle accident or a situation shortly before anaccident, the seat belt tensioner 1 (cf. FIG. 1) is activated. In thecase of an activation of this type, the drive motor 3 is put intooperation in such a manner that it retracts and tensions the seat belt2. The drive motor 3 is therefore operated in the seat belt-tensioningdirection of rotation.

The motor pinion 31 therefore rotates according to the direction ofrotation P3 according to FIG. 12. Owing to this rotation of the motorpinion 31, the connecting gearwheel 10 is rotated along the direction ofrotation P4. The coupling wheel 62 therefore drives the spindle clutchtoothed ring 61 in the direction of rotation P5. Owing to the rotationof the spindle clutch toothed ring 61, the synchronization pawl 55 willbe inserted into the pawl teeth 54 of the seat belt spindle 5 and willbring about a defined position between the spindle clutch toothed ring61 and the pawl teeth 54 of the seat belt spindle 5. Subsequently, thethree spindle clutch pawls 52 will then be inserted into the pawl teeth54 of the seat belt spindle 5 so that the spindle clutch 51 istransferred from the initially disengaged position into the engagedposition.

The function of the three spindle clutch pawls 52 is therefore to bringabout a rotational connection between the drive motor 3 and the seatbelt spindle 5 during rotation of the motor pinion 31. Before the drivemotor 3 is activated, the spindle clutch 51 is still in the uncoupledstate so that the seat belt spindle 5 can rotate entirely freely of theautomatic gear 4. The automatic gear 4 and the drive motor 3 aretherefore separated from each other before an accident or a hazardoussituation occurs with the result that the seat belt 2 can be unrolledfrom the seat belt spindle 5 without great force and therefore verycomfortably. Only in the event of an accident or a hazardous situationis the spindle clutch 51 activated with the drive motor 3 being switchedon.

After the drive motor 3 is switched on, the force transmission to theseat belt spindle 5 first takes place via the motor pinion 31, theconnecting gearwheel 10, the spindle clutch toothed ring 61, and thespindle clutch 51. That is, the first force transmission path 6according to FIG. 1 is activated. The transmission ratio of the firstforce transmission path or of the “first speed” of the automatic gear 4is, for example, 26:1. This means that the seat belt spindle 5 rotatesthrough a single revolution during 26 revolutions of the drive motor 3.

As soon as the drive motor 3 is activated and the spindle clutch toothedring 61 is rotated according to the direction of rotation P5 accordingto FIG. 12, the seat belt 2 is retracted on the seat belt spindle 5 sothat a tensioning of the seat belt occurs. With increasing tensioning ofthe seat belt, the force acting on the automatic gear 4 and thereforethe sliding clutch R becomes ever greater. As soon as the tensioningforce in the shoulder region of the vehicle occupant has reached a forceof, for example, about 200 to about 250 Newtons, the sliding clutch Rexplained in conjunction with FIG. 2 will disengage. The sliding clutchR can be seen from the lower side in FIG. 2.

If the “first” speed is active, the planetary gear 71 according to FIG.1 is rotated by the connecting gearwheel 10 and initially revolves in amanner free from force transmission. In this case, the revolving of theplanet wheel gear 71 in a manner free from force transmission ispossible since the crown wheel 713 of the planetary gear 71 can rotatefreely at the same time counter to the arrow direction P2 according toFIG. 7.

If the sliding clutch R according to FIG. 2 is now disengaged, thespindle clutch toothed ring 61 is no longer driven by the coupling wheel62. This results in the crown wheel 713 now being rotated along thedirection of rotation P2 according to FIG. 7 but this is prevented bythe planetary clutch pawl 715. Owing to the blocking of the crown wheel713, a force transmission by the planetary gear 71 now occurs so thatthe seat belt spindle 5 is now driven by the second force transmissionpath 7. In the second force transmission path 7, i.e., in the “secondspeed” of the automatic gear 4, the transmission ratio is, for example,127:1. The planetary gear 71 therefore multiplies the transmission ratiowith respect to the first speed of the automatic gear 4 by the factor4.8.

Owing to the shifting of the automatic gear 4 into the second speed, thetensioning force of the seat belt tensioner 1 is raised with the resultthat the seat belt 2 is tensioned with a great tensioning force. As soonas a predetermined tensioning force is reached and the tensioningoperation is finished, the drive motor 3 is switched off in order toprevent a further load on the electric system of the vehicle battery bythe drive motor 3. In order then to avoid the seat belt 2 from beingable to unroll again from the seat belt spindle 5, the connectinggearwheel 10 has to be blocked in the tensioning position. This takesplace by means of the blocking device 8 and the latching pawl 81, whichis initially in the first pawl position illustrated in FIGS. 8 and 9. Inthe first pawl position, the connecting gearwheel 10 can rotate in theseat belt-tensioning direction whereas an unrolling of the seat belt 2from the seat belt spindle 5 is prevented. The latching pawl 81therefore results in the tensioning force of the seat belt 2 being kept.

If, in the event of an accident, the vehicle occupant is pressed againstthe seat belt 2, the restraining force exerted by the seat belt 2 willrise severely. In order to bring about a yielding of the seat belt 2 anda restricting of the restraining force, the blocking device 8 accordingto FIG. 1 has to be switched off if a predetermined maximum seatbelt-extraction force is exceeded. This takes place in the case of theseat belt tensioner 1 by the latching pawl 81 being pivoted from thefirst pawl position illustrated in FIG. 9 into the second pawl positionillustrated in FIG. 10. The pivoting of the latching pawl 81 is possibleowing to the elongated hole 83. Owing to the latching pawl 81 beingflipped or pivoted over into the second pawl position, an unrolling ofthe seat belt 2 from the seat belt spindle 5 is subsequently possible.The further unrolling of the seat belt 2 from the seat belt spindle 5 isensured by further safety devices, for example, a torsion bar which isarranged in the interior of the seat belt spindle 5.

The seat belt tensioner 1 according to FIG. 1 is of a completelyreversible design, which means that it can be reset into its startingstate after a first commissioning. This will be explained in detailbelow with two different accident scenarios being differentiated: (a) apredetermined seat belt-extraction force has been exceeded and (b) apredetermined seat belt-extraction force has not been exceeded.

In the case of the accident scenario where a predetermined seatbelt-extraction force has been exceeded, after the seat belt has beentensioned, the predetermined seat belt-extraction force is exceeded sothat the latching pawl 81 is transferred into its second pawl position,as has been explained above in conjunction with FIGS. 8 and 9. Theresultant starting positions of the latching pawl 81, the disk cam 63,and the sliding clutch pawl 65 are once again shown in FIG. 13.

FIG. 13 also shows a connecting rod 90, which is connected rotatably toa friction element 92 via a friction element bearing pin 91. A frictionsurface 93 (e.g. rubber), which bears against a stem 94 of the disk cam63, is arranged on the outside of the friction element 92. Theconnecting rod 90 is guided on the bearing pin 82 via an elongated hole95. The position of the friction surface 93 relative to the stem 94arises due to the above-explained flipping of the latching pawl 81 overfrom the first pawl position into the second pawl position.

Since, in the case of a rotation of the motor pinion 31 (due to theplanetary gear), the coupling wheel 62, the pawl carrier 64, and thedisk cam 63 with the stem 94 will also passively rotate at the sametime, the friction surface 93 and therefore the friction element 92 arepivoted away and the connecting rod 90 is displaced in the elongatedhole 95 (cf. FIG. 13). If the drive motor is now operated once again inthe tensioning direction, then the latching pawl 81 is pivoted back intoits first pawl position (FIG. 14). As a result, the stem 94 andtherefore the disk cam 63 are rotated in relation to the pawl carrier 64counter to the spring force of the torsion spring 642 so that the cam631 is rotated back into the position illustrated in FIG. 2. The slidingclutch pawl 65 is therefore released again for engagement with theconnecting gearwheel 10.

During a further operation of the drive motor 3 in the seatbelt-tensioning direction, the sliding clutch pawl 65 will then beinserted into the connecting gearwheel 10 so that the “first” speed ofthe automatic gear 4 is activated. Since the latching pawl 81 has been“flipped over” or shifted by the drive motor 3 from its second pawlposition back into its first pawl position, a blocking of the seat belt2 after tensioning of the seat belt has taken place is possible.

For better comprehension of the operation, FIG. 15 shows the connectingrod 90, a connecting rod pin 921, the friction element 92, and thelatching pawl 81 in detail. A stop pin 96, which is fitted fixedly onthe installation plate 9, is also seen. The stop pin 96 is guided in aslotted guide of the friction element 92 and, at the end positions ofthe friction element 92, strikes against, for example, spring-mountedstops of the friction element 92.

If the predetermined seat belt-extraction force is not exceeded, thelatching pawl 81 is consequently not flipped over into the second pawlposition. The latching pawl 81 has therefore remained in its firstlatching position so that the position of the latching pawl 81 and theposition of the connecting rod 90 and of the friction element 92correspond to the position shown in FIG. 14.

In order now to move the latching pawl 81 into the non-blocking, secondpawl position and to relax the seat belt, the driving motor 3 is firstoperated in the seat belt-unrolling direction so that the latching pawl81, the connecting rod 90, and the friction element 92 are transferredinto the positions according to FIG. 13. The seat belt tensioner cantherefore be activated again.

For renewed tensioning of the seat belt, the drive motor 3 is operatedin the seat belt-tensioning direction of rotation with the result thatthe sequence of movements according to the situation where thepredetermined seat belt-extraction force has been exceeded is runthrough. As a result, the automatic gear 4 is again shifted into the“first speed” so that the first force transmission path 6 is active. Theseat belt tensioner is therefore ready for use for further tensioningsof the seat belt.

During an operation of the drive motor 3 in the seat belt-unrollingdirection, the spindle clutch toothed ring 61 is furthermore likewiserotated owing to the corresponding rotation of the connecting gearwheel10 so that the spindle clutch pawls 52 (explained in detail inconjunction with FIG. 5) can be rotated out of the pawl teeth 54 of theseat belt spindle 5 when there is a freedom from load. The same appliesto the synchronization pawl 55, which is likewise rotated out of thepawl teeth 54 of the seat belt spindle 5. Because of the rotating out ofthe three spindle clutch pawls 52 and the synchronization pawl 55, thespindle clutch 51 is disengaged so that the seat belt spindle 5 canfreely rotate. Thus, the seat belt spindle 5 is separated from theplanetary gear 71, from the second force transmission path 7, and fromthe first force transmission path 6. The synchronization pawl 55 andsubsequently the spindle clutch pawls 52 are re-engaged only when thedrive motor rotates again in the seat belt-tensioning direction ofrotation, and the spindle clutch toothed ring 61 is driven in thedirection illustrated in FIG. 5 by the designation S.

If, after the seat belt has been tensioned and the blocking device 8 hasbeen activated, an accident does not occur, contrary to expectations,because the hazardous situation could be averted, then the seat belt 2has to be able to be loosened again. This takes place in the ease of theseat belt tensioner 1 (as has already been explained above inconjunction with the reengagement of the sliding clutch R) by the drivemotor being briefly operated in the seat belt-unrolling direction. Theconnecting gearwheel 10 causes the latching pawl 81 to be “flipped over”or shifted from its first (blocking) pawl position into its second pawlposition so that the seat belt can unroll. The unrolling speed of theseat belt can be controlled, for example, with the drive motor 3 sinceits motor pinion 31 is always in engagement with the connectinggearwheel 10. Thus, by energizing the drive motor 3 in the seatbelt-tensioning direction of rotation, the unrolling of the seat beltcan be stopped.

As already mentioned, in the case of an operation of the drive motor 3in the seat belt-unrolling direction, when there is a freedom from load,the spindle clutch 51 is deactivated so that the seat belt is separatedfrom the automatic gear 4. Within the context of the latching pawl 81flipping over from the first pawl position into the second pawlposition, the seat belt force is not increased so that the occurrence ofthe otherwise customary “release peak” is avoided. That is, theswitching off of the tensioning of the seat belt is associated with nofurther increase in the seat belt restraining force for the vehicleoccupant.

Moreover, an overload clutch can be arranged between the pawl teeth 54of the seat belt spindle 5 and the seat belt spindle 5. FIG. 11 shows anexemplary embodiment of such an overload clutch. The overload clutch 100according to FIG. 11 connects the seat belt spindle 5 and the automaticgear 4 to each other. The overload clutch 100 has an overload clutchring 105. The external teeth of the overload clutch ring form the pawlteeth 54 of the seat belt spindle 5 and the inner surface of theoverload clutch ring forms an internal taper 106. In addition, theoverload clutch 100 forms an external taper 110 that is connected, forexample integrally, to the seat belt spindle 5.

The function of the internal taper 106 and of the external taper 110 isto protect the automatic gear 4 according to FIG. 1. As soon as the seatbelt spindle 5 applies a torque, which exceeds a predetermined maximumtorque to the overload clutch 100, the overload clutch 100 willinterrupt the rotational connection between the seat belt spindle 5 andthe automatic gear 4 by means of a slip.

The interruption in the coupling connection is based on the severing ofthe force-locked connection between the external taper 110 and theinternal taper 106. This is because, when the predetermined maximumtorque is exceeded, the external taper 110 will “slide” in the internaltaper 106.

The maximum torque may be preferably dimensioned in such a manner thatthe latching pawl 81 does not flip over from the first pawl positioninto the second pawl position. The latching pawl therefore remains inthe first pawl position after a tensioning of the seat belt and is onlybrought by the drive motor 3 into the second pawl position during theoperation in the seat belt-unrolling direction with the spindle clutch51 subsequently being disengaged.

The priority application, German Application DE 10-2004-012-166.4, filedon Mar. 9, 2004, including the specification, drawings, claims, andabstract, is incorporated herein by reference in its entirety.

Given the disclosure of the present invention, one versed in the artwould appreciate that there may be other embodiments and modificationswithin the scope and spirit of the invention. Accordingly, allmodifications attainable by one versed in the art from the presentdisclosure within the scope and sprit of the present invention are to beincluded as further embodiments of the present invention. The scope ofthe present invention is to be defined as set forth in the followingclaims.

1. A seat belt tensioner for a seat belt system, comprising: a seat belt spindle; a gearwheel connected to the seat belt spindle; and a latching pawl for locking the seat belt spindle in the tensioned position by engaging in teeth of the gearwheel, wherein the latching pawl is configured to be brought into a first pawl position for blocking the gearwheel in a seat belt-unrolling direction and into a second pawl position for blocking the gearwheel in a seat belt-tensioning direction of rotation, and wherein the latching pawl is configured to perform a first pivot-over operation from the first pawl position into the second pawl position and to perform a second pivot-over operation from the second pawl position into the first pawl position when the gearwheel exerts a force on the latching pawl that exceeds a predetermined force required for the respective pivoting-over operation.
 2. The seat belt tensioner according to claim 1, wherein the latching pawl is mounted in a spring-loaded manner whereby the pivoting-over of the latching pawl from the first pawl position into the second pawl position or vice versa can be triggered by a motor force of a drive motor that is connected to the gearwheel.
 3. The seat belt tensioner according to claim 1, wherein the latching pawl is configured to pivot from the first pawl position into the second pawl position when there is a predetermined seat belt-extraction force.
 4. The seat belt tensioner according to claim 1, wherein the latching pawl comprises a pivot pin arranged in an elongated hole whereby the latching pawl can be pivoted about the pivot pin.
 5. The seat-belt tensioner according to claim 4, wherein the latching pawl is configured to be deflected radially along a guide slot formed by the elongated hole.
 6. The seat belt tensioner according to claim 1, further comprising a mechanical automatic gear that shifts automatically as a function of load.
 7. The seat belt tensioner according to claim 6, wherein the automatic gear has a force transmission path for a first speed with a first transmission ratio and at least one further force transmission path for a second speed with a second transmission ratio that is larger than the first transmission ratio.
 8. The seat belt tensioner according to claim 7, wherein the gearwheel is driven by a drive motor and interacts with the first transmission path and the farther force transmission path.
 9. The seat belt tensioner according to claim 7, wherein the first force transmission path comprises a sliding clutch that disengages when a predetermined switching-off moment is exceeded, a coupling wheel that connects to the sliding clutch, and a spindle clutch toothed ring that connects to the seat belt spindle and the coupling wheel.
 10. The seat belt tensioner according to claim 9, wherein the sliding clutch has a pawl carrier that is mounted rotatably coaxially with the gearwheel and a sliding clutch pawl that is mounted pivotably on the pawl carrier whereby the sliding clutch pawl can be pivoted into a coupling position and into a disengaging position.
 11. The seat belt tensioner as claimed in claim 10, wherein the sliding clutch pawl is configured to couple the pawl carrier and the gearwheel in the seat belt-tensioning direction of rotation in its coupling position, and wherein the sliding clutch pawl is configured to be ineffective with regard to the coupling between the gearwheel and the pawl carrier in its disengaging position.
 12. A seat belt system, comprising: a seat belt; and a seat belt tensioner for a seat belt system, comprising a seat belt spindle; a gearwheel connected to the seat belt spindle; and a latching pawl for locking the seat belt spindle in the tensioned position by engaging in teeth of the gearwheel; wherein the latching pawl is configured to be brought into a first pawl position for blocking the gearwheel in a seat belt-unrolling direction and into a second pawl position for blocking the gearwheel in a seat belt-tensioning direction of rotation, and wherein the latching pawl is configured to perform a first pivot-over operation from the first pawl position into the second pawl position and to perform a second pivot-over operation from the second pawl position into the first pawl position when the gearwheel exerts a force on the latching pawl that exceeds a predetermined force required for the respective pivoting-over operation.
 13. A seat belt tensioner for a seat belt system, comprising: a seat belt spindle; a gearwheel connected to the seat belt spindle; and a latching pawl for locking the seat belt spindle in the tensioned position by engaging in teeth of the gearwheel, wherein the latching pawl is configured to be brought into a first pawl position for blocking the gearwheel in a seat belt-unrolling direction and into a second pawl position for blocking the gearwheel in a seat belt-tensioning direction of rotation, and wherein the latching pawl is held whereby said latching pawl is pivoted from the first pawl position into the second pawl position when there is a predetermined seat belt-extraction force that bears against the shoulder of the vehicle occupant.
 14. The seat belt tensioner according to claim 13, wherein the latching pawl is configured to perform a first pivot-over operation from the first pawl position into the second pawl position and to perform a second pivot-over operation from the second pawl position into the first pawl position when the gearwheel exerts a force on the latching pawl that exceeds a predetermined force required for the respective pivoting-over operation.
 15. The seat belt tensioner according to claim 13, wherein the latching pawl comprises a pivot pin arranged in an elongated hole whereby the latching pawl can be pivoted in a direction of rotation about the pivot pin.
 16. The seat belt tension according to claim 15, wherein the latching pawl is configured to be deflected radially along a guide slot formed by the elongated hole
 17. The seat belt tensioner according to claim 13, further comprising a mechanical automatic gear that shifts automatically as a function of load.
 18. The seat belt tensioner according to claim 17, wherein the automatic gear has a force transmission path for a first speed with a first transmission ratio and at least one further force transmission path for a second speed with a second transmission ratio that is larger than the first transmission ratio. 